Pattern Detection and Location in a Processed Image

ABSTRACT

The present invention is a method of processing a video image in an electronic video processor, including the steps of receiving an input image having an input field of view, generating a processed image from the input image, and having an output field of view smaller than the input field of view, searching for a predetermined pattern within the input image, providing an indication when the predetermined pattern is found in the input image, zooming the processed image to the input field of view and highlighting the predetermined pattern in the processed image in response to the indication.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 15/801,861, filed Nov. 2, 2017 for Pattern Detection andLocation in a Processed Image, which is a divisional application of U.S.patent application Ser. No. 15/357,880, filed Nov. 21, 2016, for PatternDetection and Location in a Processed Image, now U.S. Pat. No.9,842,248, which is a divisional application of U.S. patent applicationSer. No. 14/825,043, filed Aug. 12, 2015, for Pattern Detection andLocation Indication for a Visual Prosthesis, now U.S. Pat. No.9,526,896, which claims priority to, benefit of, and incorporates byreference, U.S. Provisional Application 62/036,463, filed Aug. 12, 2014for Visual Prosthesis.

FIELD OF THE INVENTION

The present invention is generally directed to an improved method ofprocessing an image.

BACKGROUND OF THE INVENTION

Detection and Tacking of Faces in Real Environments by R. Herpers, et.al. from International Workshop on Recognition, Analysis and Tracking ofFaces and Gestures in Real-Time Systems, 1999, IEEE Proceedingsdescribes basics of facial detection and recognition software forgeneral applications.

Xuming He presented an ARVO poster in 2011 describing a system for avisual prosthesis that automatically zooms in on a face in a visualscene to help a visual prosthesis user identify the face.

US Patent Application 20080058894 for Audio-tactile Vision SubstitutionSystem to Dewhurst describes providing visual information to a visionimpaired person using audio or tactile information including informationregarding facial characteristics.

International patent application WO 20010384465 for Object Tracking forArtificial Vision by Barns, et al. describes a system for trackingobjects, such as a face, for a visually impaired user.

US Patent application 20130035742 for Face Detection Tracking andRecognition for a Visual Prosthesis, the disclosure of which isincorporated herein by reference, is by the present applicants anddescribes a system for identifying a face and indicating its location tothe user of a visual prosthesis.

SUMMARY OF THE INVENTION

The present invention is a method of processing a video image in anelectronic video processor, including the steps of receiving an inputimage having an input field of view, generating a processed image fromthe input image, and having an output field of view smaller than theinput field of view, searching for a predetermined pattern within theinput image, providing an indication when the predetermined pattern isfound in the input image, zooming the processed image to the input fieldof view and highlighting the predetermined pattern in the processedimage in response to the indication.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an experimental face detection setup as seen through thecamera of a visual prosthesis with a 53 degree field of view.

FIG. 1B is a photograph of an electrode array on a retina showing the 20degree field of view covered by the electrode array.

FIG. 2A is an experimental face detection setup as seen through thecamera of a visual prosthesis, showing the narrower field of view to theelectrode array, and the electrodes stimulated by a face detectionfilter.

FIG. 2B is an experimental face detection setup as seen through thecamera of a visual prosthesis, showing the wider field of view of thecamera mapped to the electrode array, and the electrodes stimulated by aface detection filter.

FIG. 3 is a flowchart showing facial detection.

FIG. 4 is a set of three flowcharts equating face detection response tosquare localization.

FIG. 5 is a flowchart showing the process of face detection andrecognition.

FIG. 6 is a flowchart showing the process of face cueing.

FIG. 7 is a perspective view of the implanted portion of the preferredvisual prosthesis.

FIG. 8 is a side view of the implanted portion of the preferred visualprosthesis showing the strap fan tail in more detail.

FIG. 9 shows the components of a visual prosthesis fitting system.

FIG. 10a shows a LOSS OF SYNC mode.

FIG. 10b shows an exemplary block diagram of the steps taken when VPUdoes not receive back telemetry from the Retinal Stimulation System.

FIG. 10c shows an exemplary block diagram of the steps taken when theuser is not wearing the Glasses.

FIGS. 11-1, 11-2, 11-3 and 11-4 show an exemplary embodiment of a videoprocessing unit. FIG. 11-1 should be viewed at the left of FIG. 11-2.FIG. 11-3 should be viewed at the left of FIG. 11-4. FIGS. 11-1 and 11-2should be viewed on top of FIGS. 11-3 and 11-4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description is of the best mode presently contemplated forcarrying out the invention. This description is not to be taken in alimiting sense, but is made merely for the purpose of describing thegeneral principles of the invention. The scope of the invention shouldbe determined with reference to the claims.

An aspect of the invention is a method of aiding a visual prosthesisuser, including detecting a face in the user's visual scene andcommunicating the location of the detected face, including zooming outto show the location of the detected face through a highlight; andproviding cues to the user regarding a detected face. The cue mayinclude sound, vibration, stating a name associated with the detectedface, highlighting the detected face, zooming in on the detected face,or tactile feedback. The method may further include looking up thedetected face in a look up table to provide a name associated with thedetected face. The cue may further include an indication of if the faceis looking toward the user, to the side or looking away. A furtheraspect of the invention is including information about a facialcharacteristic in the cue. Facial characteristics may include gender,size, distance, head movement, or other body motion. All of thesecharacteristics are controllable by the user through controls on thevideo processing unit worn on the body.

Referring to FIG. 1, The currently available visual prosthesis providesan electrode array 10 which stimulates the retina to provide a field ofview of 20 degrees (FIG. 1A) while a camera provides a 53 degree fieldof view (FIG. 1B). While larger arrays are desirable and will beavailable in the future, it is clear that camera technology will alwayssurpass electrode array technology. Zoom systems have been provided invisual prostheses. A one to one ratio is best for locomotion and handeye coordination as described in US-2008-0183244-M, Field of ViewMatching in a Visual Prosthesis. It is also known that zoom in can bebeneficial for tasks such as reading. However, the facial detection taskbenefits from a wider angle view. It is often beneficial for a visualprosthesis user to know the location of faces within a scene. Thosefaces can be identified with a simple highlight or only stimulating thelocation of the face. In such case a wider field of view supportsfinding faces quickly. It should be clear that while described inrelation to facial detection, any pattern of interest can be detectedand its location identified by the same method. Patterns of interest mayinclude, for example, stumble or trip hazards, automobiles, doors,windows or faces.

It is not necessary to zoom the user's view to detect and identify suchpatterns. In this example, the camera views 53 degrees while only 20degrees is presented to the user through an electrode array. Softwarecan be constantly scanning the 53 degree image and notifying the userwhen a pattern of interest is detected in the scene. When a pattern ofinterest is detected, the system can zoom out and cue a user, or cue auser and wait for the user to zoom out manually. It is important to notchange the field of view without the user's knowledge.

This function can be further combined with recognition functions such aslooking up a detected face and speaking the name associated with theface. Alternatively, the system can describe characteristics of theface.

Referring to FIG. 2, the experimental face detection setup is shown asseen through the camera of a visual prosthesis, showing the narrowerfield of view 2000 to the electrode array 10. A face is detected 2002and electrodes stimulated by a face detection filter 2004. Theadditional information provided by the face detection filter is minimal.A visual prosthesis user will need to scan the scene through the 20degree view until a face is detected. At this level the visualprosthesis user would probably be able to detect a face without thefilter.

Referring to FIG. 2B, the experimental face detection setup is shown asseen through the camera of a visual prosthesis. In this case, the widerfield of view of the camera is mapped to the electrode array 10. A faceis detected 2006 by a face detection filter and electrodes arestimulated 2008. With the wider field of view, the visual prosthesisuser is able to identify the location of a face within the scene withminimal or no scanning. Preferably, a visual prosthesis user would beable to switch modes quickly and easily. For example, a single buttoncould be provided on the VPU which shifts to the wider field of view andactivating the face detection software. Releasing the button wouldreturn the visual prosthesis to the previous mode. This allows the user,when entering a room for example, to quickly indentify the location offaces in the room.

While described in terms of face detection, the present invention, inparticular as it applies to wide field of view, is also applicable towide range of other uses, such as hazard detection. Any item that can bedetected by the visual prosthesis camera and image processing softwarecan be readily identified with the present invention. As anotherexample, when combined with an infrared camera, heat sources can beidentified.

The following table shows face detection response times in a clinicaltrial.

User ID Wide FOV (53 deg.) Normal FOV (20 deg.) 1 38 ± 4  53 ± 12 2 20 ±2 42 ± 5 3  5 ± 1 11 ± 3 4 12 ± 2 22 ± 4The times are in seconds based on 10 trials for each user after 10practice trials. Another trial was conducted with and without a target(target turned away not showing their face.

User ID Mean Response Time 1 5.2 ± .9 2 6.4 ± .7

Referring to FIG. 3, simple face tracking can be a significant benefitto a blind person. The presence of multiple faces may be also relayed.The process flow of basic face detection and tracking is provided. Thevideo processor records a visual scene 102, show here with two faces.The video processor draws a square around a detected face 104. The videoprocessor draws squares around both face units and draws a smallersquare around the identifiable portions of the two faces for recognitionprocessing 106. Even with a very low resolution electrode array, it ispossible for a user to locate the faces 108 to improve interaction withthe other people.

Referring to FIG. 4, square localization is a common task preformed byvisual prosthesis users. See US Patent Application 2010/0249878, forVisual Prosthesis Fitting Training and Assessment System and Method,filed Mar. 26, 2010 which is incorporated herein by reference. Providinga square over a detected face, simplifies the face tracking to the levelof square localization. In the first example 110, the face isindentified at an angle. It may be advantageous to straighten the squareto improve user recognition. In the second example 112, the face isoutside the visual scene so no highlight is provided. In the thirdexample 114, the face square is simply highlighted without modification.The distance to the person, distance direction and velocity may also berelayed to the user.

Referring to FIG. 5, the process of face detection begins by scanningthe input image from the camera for a pattern of a face 202. There aremany well known processes for indentifying faces in an image. If a faceis detected, it is compared to a database of known faces 204. If theface is unknown, the face is cued 208 as described in greater detail inFIG. 6. If the face is known, it is announced 206. Finally, facialcharacteristics are determined 210.

Referring to FIG. 6, there are several options for cueing the presenceof an unknown face which are selectable by the user. The user can changethe selection by activating controls on the VPU 20. The systemdetermines if Highlight is selected 302, and highlights the face 304. Ina low resolution visual prosthesis this can be accomplished simply byreplacing the face with a bright image. In a higher resolution visualprosthesis this may be accomplished by marking a square or circle aroundthe face. Alternatively, if Zoom is selected 306, the visual prosthesiszooms in on the face aiding the user in identifying the face 308, orzooming out to provide the location of the face. If Vibration isselected 310, the visual processing unit vibrates (like a cell phone insilent mode) 312. If Tone is selected 314, the speaker on the visualprosthesis emits a tone 316. Note that the cues may be used incombination such as highlight, vibrate and tone.

FIGS. 7 and 8 present the general structure of a visual prosthesis usedin implementing the invention.

FIG. 7 shows a perspective view of the implanted portion of thepreferred visual prosthesis. A flexible circuit 1 includes a flexiblecircuit electrode array 10 which is mounted by a retinal tack (notshown) or similar means to the epiretinal surface. The flexible circuitelectrode array 10 is electrically coupled by a flexible circuit cable12, which pierces the sclera and is electrically coupled to anelectronics package 14, external to the sclera.

The electronics package 14 is electrically coupled to a secondaryinductive coil 16. Preferably the secondary inductive coil 16 is madefrom wound wire. Alternatively, the secondary inductive coil 16 may bemade from a flexible circuit polymer sandwich with wire traces depositedbetween layers of flexible circuit polymer. The secondary inductive coilreceives power and data from a primary inductive coil 17, which isexternal to the body. The electronics package 14 and secondary inductivecoil 16 are held together by the molded body 18. The molded body 18holds the electronics package 14 and secondary inductive coil 16 end toend. The secondary inductive coil 16 is placed around the electronicspackage 14 in the molded body 18. The molded body 18 holds the secondaryinductive coil 16 and electronics package 14 in the end to endorientation and minimizes the thickness or height above the sclera ofthe entire device. The molded body 18 may also include suture tabs 20.The molded body 18 narrows to form a strap 22, which surrounds thesclera and holds the molded body 18, secondary inductive coil 16 andelectronics package 14 in place. The molded body 18, suture tabs 20 andstrap 22 are preferably an integrated unit made of silicone elastomer.Silicone elastomer can be formed in a pre-curved shape to match thecurvature of a typical sclera. However, silicone remains flexible enoughto accommodate implantation and to adapt to variations in the curvatureof an individual sclera. The secondary inductive coil 16 and molded body18 are preferably oval shaped. A strap 22 can better support an ovalshaped coil. It should be noted that the entire implant is attached toand supported by the sclera. An eye moves constantly. The eye moves toscan a scene and also has a jitter motion to improve acuity. Even thoughsuch motion is useless in the blind, it often continues long after aperson has lost their sight. By placing the device under the rectusmuscles with the electronics package in an area of fatty tissue betweenthe rectus muscles, eye motion does not cause any flexing which mightfatigue, and eventually damage, the device.

FIG. 8 shows a side view of the implanted portion of the visualprosthesis, in particular, emphasizing the fan tail 24. When implantingthe visual prosthesis, it is necessary to pass the strap 22 under theeye muscles to surround the sclera. The secondary inductive coil 16 andmolded body 18 must also follow the strap 22 under the lateral rectusmuscle on the side of the sclera. The implanted portion of the visualprosthesis is very delicate. It is easy to tear the molded body 18 orbreak wires in the secondary inductive coil 16. In order to allow themolded body 18 to slide smoothly under the lateral rectus muscle, themolded body 18 is shaped in the form of a fan tail 24 on the endopposite the electronics package 14. The strap 22 further includes ahook 28 that aids the surgeon in passing the strap under the rectusmuscles.

Referring to FIG. 9, a Fitting System (FS) may be used to configure andoptimize the visual prosthesis 3 of the Retinal Stimulation System 1.

The Fitting System may comprise custom software with a Graphical UserInterface (GUI) running on a dedicated laptop computer 10. Within theFitting System are modules for performing diagnostic checks of theimplant, loading and executing video configuration files, viewingelectrode voltage waveforms, and aiding in conducting psychophysicalexperiments. A video module can be used to download a videoconfiguration file to a Video Processing Unit (VPU) 20 and store it innon-volatile memory to control various aspects of video configuration,e.g. the spatial relationship between the video input and theelectrodes. The software can also load a previously used videoconfiguration file from the VPU 20 for adjustment.

The Fitting System can be connected to the Psychophysical Test System(PTS), located, for example, on a dedicated laptop 30, in order to runpsychophysical experiments. In psychophysics mode, the Fitting Systemenables individual electrode control, permitting clinicians to constructtest stimuli with control over current amplitude, pulse-width, andfrequency of the stimulation. In addition, the psychophysics moduleallows the clinician to record user responses. The PTS may include acollection of standard psychophysics experiments, developed using, forexample, MATLAB (MathWorks) software and other tools, to allow theclinicians to develop customized psychophysics experiment scripts.

Any time stimulation is sent to the VPU 20, the stimulation parametersare checked to ensure that maximum charge per phase limits, chargebalance, and power limitations are met before the test stimuli are sentto the VPU 20 to make certain that stimulation is safe.

Using the psychophysics module, important perceptual parameters, such asperceptual threshold, maximum comfort level, and spatial location ofpercepts, may be reliably measured.

Based on these perceptual parameters, the fitting software enablescustom configuration of the transformation between video image andspatio-temporal electrode stimulation parameters in an effort tooptimize the effectiveness of the visual prosthesis for each user.

The Fitting System laptop 10 is connected to the VPU 20 using anoptically isolated serial connection adapter 40. Because it is opticallyisolated, the serial connection adapter 40 assures that no electricleakage current can flow from the Fitting System laptop 10.

As shown in FIG. 9, the following components may be used with theFitting System according to the present disclosure. A Video ProcessingUnit (VPU) 20 for the user being tested, a Charged Battery 25 for theVPU 20, Glasses 5, a Fitting System (FS) laptop 10, a PsychophysicalTest System (PTS) laptop 30, a PTS CD (not shown), a CommunicationAdapter (CA) 40, a USB Drive (Security) (not shown), a USB Drive(Transfer) (not shown), a USB Drive (Video Settings) (not shown), a UserInput Device (RF Tablet) 50, a further User Input Device (Jog Dial) 55,Glasses Cable 15, CA-VPU Cable 70, CFS-CA Cable 45, CFS-PTS Cable 46,Four (4) Port USB Hub 47, Mouse 60, LED Test Array 80, Archival USBDrive 49, an Isolation Transformer (not shown), adapter cables (notshown), and an External Monitor (not shown).

The external components of the Fitting System according to the presentdisclosure may be configured as follows. The battery 25 is connectedwith the VPU 20. The PTS laptop 30 is connected to FS laptop 10 usingthe CFS-PTS Cable 46. The PTS laptop 30 and FS laptop 10 are pluggedinto the Isolation Transformer (not shown) using the Adapter Cables (notshown). The Isolation Transformer is plugged into the wall outlet. Thefour (4) Port USB Hub 47 is connected to the FS laptop 10 at the USBport. The mouse 60 and the two User Input Devices 50 and 55 areconnected to four (4) Port USB Hubs 47. The FS laptop 10 is connected tothe Communication Adapter (CA) 40 using the CFS-CA Cable 45. The CA 40is connected to the VPU 20 using the CA-VPU Cable 70. The Glasses 5 areconnected to the VPU 20 using the Glasses Cable 15.

Stand-Alone Mode

Referring to FIG. 10, in the stand-alone mode, the video camera 13 onthe Glasses 5 captures a video image that is sent to the VPLJ 20. TheVPU 20 processes the image from the camera 13 and transforms it intoelectrical stimulation patterns that are transmitted to the externalcoil 17. The external coil 17 sends the electrical stimulation patternsand power via radio-frequency (RF) telemetry to the implanted RetinalStimulation System. The internal coil 16 of the Retinal StimulationSystem receives the RF commands from the external coil 17 and transmitsthem to the electronics package 14 that in turn delivers stimulation tothe retina via the electrode array 10. Additionally, the RetinalStimulation System may communicate safety and operational status back tothe VPU 20 by transmitting RF telemetry from the internal coil 16 to theexternal coil 17. The visual prosthesis apparatus may be configured toelectrically activate the Retinal Stimulation System only when it ispowered by the VPU 20 through the external coil 17. The stand-alone modemay be used for clinical testing and/or at-home use by the user.

Communication Mode

The communication mode may be used for diagnostic testing,psychophysical testing, user fitting and downloading of stimulationsettings to the VPU 20 before transmitting data from the VPU 20 to theretinal stimulation system, as is done, for example, in the stand-alonemode described above. Referring to FIG. 9, in the communication mode,the VPU 20 is connected to the Fitting System (FS) laptop 21 usingcables 70, 45 and the optically isolated serial connection adapter 40.In this mode, laptop 21 generated stimuli may be presented to the userand programming parameters may be adjusted and downloaded to the VPU 20.The Psychophysical Test System (PTS) laptop 30 connected to the FittingSystem (FS) laptop 21 may also be utilized to perform more sophisticatedtesting and analysis as fully described in the related application, U.S.Pat. No. 8,271,091, (Applicant's Docket No. S401-USA) which isincorporated herein by reference in its entirety.

In one embodiment, the functionality of the Retinal Stimulation Systemcan also be tested pre-operatively and intra-operatively (i.e. beforeoperation and during operation) by using an external coil 17 without theGlasses 5, placed in close proximity to the Retinal Stimulation System.The coil 17 may communicate the status of the Retinal Stimulation Systemto the VPU 20 that is connected to the Fitting System laptop 21 as shownin FIG. 9.

As discussed above, the VPU 20 processes the image from the camera 13and transforms the image into electrical stimulation patterns for theRetinal Stimulation System. Filters, such as edge detection filters, maybe applied to the electrical stimulation patterns, for example, by theVPU 20, to generate, for example, a stimulation pattern based onfiltered video data that the VPU 20 turns into stimulation data for theRetinal Stimulation System. The images may then be reduced in resolutionusing a downscaling filter. In one exemplary embodiment, the resolutionof the image may be reduced to match the number of electrodes in theelectrode array 10 of the Retinal Stimulation System. That is, if theelectrode array has, for example, sixty electrodes, the image may bereduced to a sixty channel resolution. After the reduction inresolution, the image is mapped to stimulation intensity using, forexample, a look-up table that has been derived from testing ofindividual users. Then the VPU 20 transmits the stimulation parametersvia forward telemetry to the Retinal Stimulation System in frames thatmay employ a cyclic redundancy check (CRC) error detection scheme.

In one exemplary embodiment, the VPU 20 may be configured to allow theuser i) to turn the visual prosthesis apparatus on and off, ii) tomanually adjust settings, and iii) to provide power and data to theRetinal Stimulation System. Referring again to FIGS. 1 through 4, theVPU 20 may comprise a case and buttons 6, including a power button forturning the VPU 20 on and off, a setting button and zoom buttons forcontrolling the camera 13, temple extensions 8 for connecting to theGlasses 5, a connector port for connecting to the laptop 21 through theconnection adapter 40, one or more indicator lights (not shown) on theVPU 20 or Glasses 5 to give visual indication of the operating status ofthe system, the rechargeable battery (not shown) for powering the VPU20, battery latch (not shown) for locking the battery in the case,digital circuit boards (not shown), and a speaker (not shown) to provideaudible alerts to indicate various operational conditions of the system.Because the VPU 20 is used and operated by a person with minimal or novision, the buttons on the VPU 20 may be differently shaped and/or havespecial markings to help the user identify the functionality of thebutton without having to look at it.

In one embodiment, the indicator lights may indicate that the VPU 20 isgoing through system start-up diagnostic testing when the one or moreindicator lights are blinking fast (more than once per second) and aregreen in color. The indicator lights may indicate that the VPU 20 isoperating normally when the one or more indicator lights are blinkingonce per second and are green in color. The indicator lights mayindicate that the Retinal Stimulation System has a problem that wasdetected by the VPU 20 during the start-up diagnostic when the one ormore indicator lights are blinking, for example, once in every fiveseconds, and are green in color. The indicator lights may indicate thatthere is a loss of communication between the Retinal Stimulation Systemand the external coil 17 due to the movement or removal of the Glasses 5while the system is operational, or if the VPU 20 detects a problem withthe Retinal Stimulation System and shuts off power to the RetinalStimulation System when the one or more indicator lights are always onand are orange color. One skilled in the art would appreciate that othercolors and blinking patterns can be used to give visual indication ofthe operating status of the system without departing from the spirit andscope of the invention.

In one embodiment, a single short beep from the speaker (not shown) maybe used to indicate that one of the buttons 6 have been pressed. Asingle beep followed by two more beeps from the speaker (not shown) maybe used to indicate that the VPU 20 is turned off. Two beeps from thespeaker (not shown) may be used to indicate that the VPU 20 is startingup. Three beeps from the speaker (not shown) may be used to indicatethat an error has occurred and the VPU 20 is about to shut downautomatically. As would be clear to one skilled in the art, differentperiodic beeping may also be used to indicate a low battery voltagewarning, that there is a problem with the video signal, and/or there isa loss of communication between the Retinal Stimulation System and theexternal coil 17. One skilled in the art would appreciate that othersounds can be used to give audio indication of the operating status ofthe system without departing from the spirit and scope of the invention.For example, the beeps may be replaced by an actual prerecorded voiceindicating the operating status of the system.

In one exemplary embodiment, the VPU 20 is in constant communicationwith the Retinal Stimulation System through forward and backwardtelemetry. In this document, the forward telemetry refers totransmission from the VPU 20 to the Retinal Stimulation System and thebackward telemetry refers to transmissions from the Retinal StimulationSystem to the VPU 20. During the initial setup, the VPU 20 may transmitnull frames (containing no stimulation information) until the VPU 20synchronizes with the Retinal Stimulation System via the back telemetry.In one embodiment, an audio alarm may be used to indicate whenever thesynchronization has been lost.

In order to supply power and data to the Retinal Stimulation System, theVPU 20 may drive the external coil 17, for example, with a 3 MHz signal.To protect the user, the Retinal Stimulation System may comprise afailure detection circuit to detect direct current leakage and to notifythe VPU 20 through back telemetry so that the visual prosthesisapparatus can be shut down.

The forward telemetry data (transmitted for example at 122.76 kHz) maybe modulated onto the exemplary 3 MHz carrier using Amplitude ShiftKeying (ASK), while the back telemetry data (transmitted for example at3.8 kHz) may be modulated using Frequency Shift Keying (FSK) with, forexample, 442 kHz and 457 kHz. The theoretical bit error rates can becalculated for both the ASK and FSK scheme assuming a ratio of signal tonoise (SNR). The system disclosed in the present disclosure can bereasonably expected to see bit error rates of 10-5 on forward telemetryand 10-3 on back telemetry. These errors may be caught more than 99.998%of the time by both an ASIC hardware telemetry error detection algorithmand the VPU's firmware. For the forward telemetry, this is due to thefact that a 16-bit cyclic redundancy check (CRC) is calculated for every1024 bits sent to the ASIC within electronics package 14 of the RetinalStimulation System. The ASIC of the Retinal Stimulation System verifiesthis CRC and handles corrupt data by entering a non-stimulating ‘safe’state and reporting that a telemetry error was detected to the VPU 20via back telemetry. During the ‘safe’ mode, the VPU 20 may attempt toreturn the implant to an operating state. This recovery may be on theorder of milliseconds. The back telemetry words are checked for a 16-bitheader and a single parity bit. For further protection against corruptdata being misread, the back telemetry is only checked for header andparity if it is recognized as properly encoded Biphase Mark Encoded(BPM) data. If the VPU 20 detects invalid back telemetry data, the VPU20 immediately changes mode to a ‘safe’ mode where the RetinalStimulation System is reset and the VPU 20 only sends non-stimulatingdata frames. Back telemetry errors cannot cause the VPU 20 to doanything that would be unsafe.

The response to errors detected in data transmitted by VPU 20 may beginat the ASIC of the Retinal Stimulation System. The Retinal StimulationSystem may be constantly checking the headers and CRCs of incoming dataframes. If either the header or CRC check fails, the ASIC of the RetinalStimulation System may enter a mode called LOSS OF SYNC 950, shown inFIG. 10a . In LOSS OF SYNC mode 950, the Retinal Stimulation System willno longer produce a stimulation output, even if commanded to do so bythe VPU 20. This cessation of stimulation occurs after the end of thestimulation frame in which the LOSS OF SYNC mode 950 is entered, thusavoiding the possibility of unbalanced pulses not completingstimulation. If the Retinal Stimulation System remains in a LOSS OF SYNCmode 950 for 1 second or more (for example, caused by successive errorsin data transmitted by the VPU 20), the ASIC of the Retinal StimulationSystem disconnects the power lines to the stimulation pulse drivers.This eliminates the possibility of any leakage from the power supply ina prolonged LOSS OF SYNC mode 950. From the LOSS OF SYNC mode 950, theRetinal Stimulation System will not re-enter a stimulating mode until ithas been properly initialized with valid data transmitted by the VPU 20.

In addition, the VPU 20 may also take action when notified of the LOSSOF SYNC mode 950. As soon as the Retinal Stimulation System enters theLOSS OF SYNC mode 950, the Retinal Stimulation System reports this factto the VPU 20 through back telemetry. When the VPU 20 detects that theRetinal Stimulation System is in LOSS OF SYNC mode 950, the VPU 20 maystart to send ‘safe’ data frames to the Retinal Stimulation System.‘Safe’ data is data in which no stimulation output is programmed and thepower to the stimulation drivers is also programmed to be off. The VPU20 will not send data frames to the Retinal Stimulation System withstimulation commands until the VPU 20 first receives back telemetry fromthe Retinal Stimulation System indicating that the Retinal StimulationSystem has exited the LOSS OF SYNC mode 950. After several unsuccessfulretries by the VPU 20 to take the implant out of LOSS OF SYNC mode 950,the VPU 20 will enter a Low Power Mode (described below) in which theimplant is only powered for a very short time. In this time, the VPU 20checks the status of the implant. If the implant continues to report aLOSS OF SYNC mode 950, the VPU 20 turns power off to the RetinalStimulation System and tries again later. Since there is no possibilityof the implant electronics causing damage when it is not powered, thismode is considered very safe.

Due to an unwanted electromagnetic interference (EMI) or electrostaticdischarge (ESD) event, the VPU 20 data, specifically the VPU firmwarecode in RAM, can potentially get corrupted and may cause the VPU 20firmware to freeze. As a result, the VPU 20 firmware will stop resettingthe hardware watchdog circuit, which may cause the system to reset. Thiswill cause the watchdog timer to expire causing a system reset in, forexample, less than 2.25 seconds. Upon recovering from the reset, the VPU20 firmware logs the event and shuts itself down. The VPU 20 will notallow system usage after this occurs once. This prevents the VPU 20 codefrom freezing for extended periods of time and hence reduces theprobability of the VPU sending invalid data frames to the implant.

Supplying power to the Retinal Stimulation System can be a significantportion of the VPU 20's total power consumption. When the RetinalStimulation System is not within receiving range to receive either poweror data from the VPU 20, the power used by the VPU 20 is wasted.

Power delivered to the Retinal Stimulation System may be dependent onthe orientation of the coils 17 and 16. The power delivered to theRetinal Stimulation System may be controlled, for example, via the VPU20, every 16.6 ms. The Retinal Stimulation System may report how muchpower it receives and the VPU 20 may adjust the power supply voltage ofthe RF driver to maintain a required power level on the RetinalStimulation System. Two types of power loss may occur: 1) long term (>˜1second) and 2) short term (<˜1 second). The long term power loss may becaused, for example, by a user removing the Glasses 5.

In one exemplary embodiment, the Low Power Mode may be implemented tosave power for the VPU 20. The Low Power Mode may be entered, forexample, anytime the VPU 20 does not receive back telemetry from theRetinal Stimulation System. Upon entry into the Low Power Mode, the VPU20 turns off power to the Retinal Stimulation System. After that, andperiodically, the VPU 20 turns power back on to the Retinal StimulationSystem for an amount of time just long enough for the presence of theRetinal Stimulation System to be recognized via its back telemetry. Ifthe Retinal Stimulation System is not immediately recognized, thecontroller again shuts off power to the Retinal Stimulation System. Inthis way, the controller ‘polls’ for the passive Retinal StimulationSystem and a significant reduction in power used is seen when theRetinal Stimulation System is too far away from its controller device.FIG. 10b depicts an exemplary block diagram 900 of the steps taken whenthe VPU 20 does not receive back telemetry from the Retinal StimulationSystem. If the VPU 20 receives back telemetry from the RetinalStimulation System (output “YES” of step 901), the Retinal StimulationSystem may be provided with power and data (step 906). If the VPU 20does not receive back telemetry from the Retinal Stimulation System(output “NO” of step 901), the power to the Retinal Stimulation Systemmay be turned off. After some amount of time, power to the RetinalStimulation System may be turned on again for enough time to determineif the Retinal Stimulation System is again transmitting back telemetry(step 903). If the Retinal Stimulation System is again transmitting backtelemetry (step 904), the Retinal Stimulation System is provided withpower and data (step 906). If the Retinal Stimulation System is nottransmitting back telemetry (step 904), the power to the RetinalStimulation System may again be turned off for a predetermined amount oftime (step 905) and the process may be repeated until the RetinalStimulation System is again transmitting back telemetry.

In another exemplary embodiment, the Low Power Mode may be enteredwhenever the user is not wearing the Glasses 5. In one example, theGlasses 5 may contain a capacitive touch sensor (not shown) to providethe VPU 20 digital information regarding whether or not the Glasses 5are being worn by the user. In this example, the Low Power Mode may beentered whenever the capacitive touch sensor detects that the user isnot wearing the Glasses 5. That is, if the user removes the Glasses 5,the VPU 20 will shut off power to the external coil 17. As soon as theGlasses 5 are put back on, the VPU 20 will resume powering the externalcoil 17. FIG. 10c depicts an exemplary block diagram 910 of the stepstaken when the capacitive touch sensor detects that the user is notwearing the Glasses 5. If the user is wearing the Glasses 5 (step 911),the Retinal Stimulation System is provided with power and data (step913). If the user is not wearing the Glasses 5 (step 911), the power tothe Retinal Stimulation System is turned off (step 912) and the processis repeated until the user is wearing the Glasses 5.

One exemplary embodiment of the VPU 20 is shown in FIGS. 11-1 to 11-4.The VPU 20 may comprise: a Power Supply Distribution and MonitoringCircuit (PSDM) 1005, a Reset Circuit 1010, a System Main Clock (SMC)source (not shown), a Video Preprocessor Clock (VPC) source (not shown),a Digital Signal Processor (DSP) 1020, Video Preprocessor Data Interface1025, a Video Preprocessor 1075, an I²C Protocol Controller 1030, aComplex Programmable Logic device (CPLD) (not shown), a ForwardTelemetry Controller (FTC) 1035, a Back Telemetry Controller (BTC) 1040,Input/Output Ports 1045, Memory Devices like a Parallel Flash Memory(PFM) 1050 and a Serial Flash Memory (SFM) 1055, a Real Time Clock 1060,an RF Voltage and Current Monitoring Circuit (VIMC) (not shown), aspeaker and/or a buzzer (not shown), an RF receiver 1065, and an RFtransmitter 1070.

The Power Supply Distribution and Monitoring Circuit (PSDM) 1005 mayregulate a variable battery voltage to several stable voltages thatapply to components of the VPU 20. The Power Supply Distribution andMonitoring Circuit (PSDM) 1005 may also provide low battery monitoringand depleted battery system cutoff. The Reset Circuit 1010 may havereset inputs 1011 that are able to invoke system level rest. Forexample, the reset inputs 1011 may be from a manual push-button reset, awatchdog timer expiration, and/or firmware based shutdown. The SystemMain Clock (SMC) source is a clock source for the DSP 1020 and CPLD. TheVideo Preprocessor Clock (VPC) source is a clock source for the VideoProcessor. The DSP 1020 may act as the central processing unit of theVPU 20. The DSP 1020 may communicate with the rest of the components ofthe VPU 20 through parallel and serial interfaces. The Video Processor1075 may convert the NTSC signal from the camera 13 into a down-scaledresolution digital image format. The Video Processor 1075 may comprise avideo decoder (not shown) for converting the NTSC signal into ahigh-resolution digitized image and a video scaler (not shown) forscaling down the high-resolution digitized image from the video decoderto an intermediate digitized image resolution. The video decoder may becomposed of an Analog Input Processing, Chrominance and LuminanceProcessing and Brightness Contrast and Saturation (BCS) Controlcircuits. The video scaler may be composed of Acquisition control,Pre-scaler, BCS-control, Line Buffer and Output Interface. The I²CProtocol Controller 1030 may serve as a link between the DSP 1020 andthe I²C bus. The I²C Protocol Controller 1030 may be able to convert theparallel bus interface of the DSP 1020 to the I²C protocol bus or viceversa. The I²C Protocol Controller 1030 may also be connected to theVideo Processor 1075 and the Real Time Clock 1060. The VPDI 1025 maycontain a tri-state machine to shift video data from the VideoPreprocessor 1075 to the DSP 1020. The Forward Telemetry Controller(FTC) 1035 packs 1024 bits of forward telemetry data into a forwardtelemetry frame. The FTC 1035 retrieves the forward telemetry data fromthe DSP 1020 and converts the data from logic level to biphase markeddata. The Back Telemetry Controller (BTC) 1040 retrieves the biphasemarked data from the RF receiver 1065, decodes it, and generates theBFSR, BCLKR and BDR for the DSP 1020. The Input/Output Ports 1045provide expanded JO functions to access the CPLD on-chip and off-chipdevices. The Parallel Flash Memory (PFM) 1050 may be used to storeexecutable code and the Serial Flash Memory (SFM) 1055 may provide aSerial Port Interface (SPI) for data storage. The VIMC may be used tosample and monitor RF transmitter 1070 current and voltage in order tomonitor the integrity status of the Retinal Stimulation System.

Accordingly, what has been shown is an improved visual prosthesis. Whilethe invention has been described by means of specific embodiments andapplications thereof, it is understood that numerous modifications andvariations could be made thereto by those skilled in the art withoutdeparting from the spirit and scope of the invention. It is therefore tobe understood that within the scope of the claims, the invention may bepracticed otherwise than as specifically described herein.

What we claim is:
 1. A visual prosthesis comprising: an infrared camerasuitable to be external to the body; a video processing unit receivingvideo data from the camera and producing stimulation codes indicatingelectrode patterns to be presented; the video processing unit includinga pattern detection component; a wireless transmitter receiving codesfrom the video processing unit and transmitting the codes; animplantable wireless receiver suitable to be implanted within a body,receiving the codes from the wireless transmitter; an implantable signalgenerator receiving the codes from the wireless receiver and generatingstimulation signals; and an implantable electrode array receiving thestimulation signals and suitable to stimulate visual neural tissue;wherein the pattern detection component provides an indication of thelocation of a detected pattern in the stimulation signal.
 2. The visualprosthesis according to claim 1, wherein the pattern detection componentdetects faces.
 3. The visual prosthesis according to claim 1, whereinthe pattern detection component detects heat hazards.
 4. The visualprosthesis according to claim 1, further comprising a zoom componentadapted to zoom out when the pattern is detected in an input field ofview of the video data, but not an output field of view defined by thestimulation signals.
 5. The visual prosthesis according to claim 4,wherein the zoom component and pattern detection component are manuallyoperable.
 6. The visual prosthesis according to claim 4, wherein thepattern detection component is continuous and cues a user to manuallyoperate the zoom component.
 7. The visual prosthesis according to claim4, wherein the pattern detection component is continuous andautomatically activates the zoom component in response to a detectedpattern.
 8. The visual prosthesis according to claim 7, wherein thevisual prosthesis cues a user in response to the zoom component beingautomatically activated.
 9. The visual prosthesis according to claim 1,further comprising a pattern recognition component recognizing featuresof the detected pattern.
 10. The visual prosthesis according to claim 9,wherein the pattern recognition component includes a look up table ofpatterns and identifying information.
 11. The visual prosthesisaccording to claim 10, wherein the look up table associates faces withnames.
 12. The visual prosthesis according to claim 11, furthercomprising an enunciator to announce a name associated with a detectedface.
 13. The visual prosthesis according to claim 1, further comprisinga visible light camera, wherein the video processing unit combines videodata from the infrared camera and the visible light camera.